MAHLER: SYMPHONY NO. 1. Philadelphia Orchestra conducted by Riccardo Muti. Angel 39078 (digital). Muti's new recording of Mahler's First displays his several strengths as a conductor. His rhythms are taut, hard-driven but bouncy, too. He balances his gestures; he knows what is coming up and prepares for it. But these effects merely decorate the surface of Mahler's symphony, as though Muti were hanging gaudy baubles on an essentially plain garment. The Philadelphia Orchestra, especially the winds, points up the melodies and the odd rhythms expertly but lacks insightful direction.